How long do I roast my pork for?

[3ismylot]

Hi all am hoping you can help me, I have bought a lovely looking 1.6kg joint of boneless pork shoulder and want to roast it for dinner but dont know how long to cook it for??
Is there a rule of time per lb?

TIA

Hi it's usually 30 minutes per pound and 30 minutes extra, at 180 degrees. And a pound is 450g!

i dont like shoulder pork as a rule but i love it like this

but it may be a bit late to start now!